User manual

Table Of Contents
Zynq-7000 AP SoC Technical Reference Manual www.xilinx.com 188
UG585 (v1.11) September 27, 2016
Chapter 6: Boot and Configuration
Boot Page Access
When the SD card is reset, it defaults to providing access to the boot page. The BootROM assumes
that the boot page is accessible when it executes. If user code changes to a different page and a Zynq
system reset occurs without resetting the SD card, then the BootROM will not be able to read the
BootROM Header from the boot page of the SD card.
BootROM Header Search and Multiboot
In SD card boot mode, the BootROM does not perform a header search and does not support
multiboot.
Boot Time Optimizations
To improve the boot time of SD card, set the CPU clock divider to 2 instead of 4. The setting assumes
a 33 MHz PS_CLK. If a faster clock is used, then a larger divider must be considered.
6.3.8 JTAG Boot
There are two JTAG controllers in the Zynq device: the TAP and DAP controllers. The test access port
(TAP) controller can control the PL configuration process and other functions in the PL. Detailed
information regarding the TAP controller can be found in UG470
, 7 Series FPGAs Configuration User
Guide. The debug access port (DAP) controller is in the application processing unit (APU), see
Chapter 3, Application Processing Unit. Detailed DAP controller information can be found in
Chapter 27, JTAG and DAP Subsystem. There are two chaining modes to access these JTAG
controllers: cascade and independent modes, as shown in Figure 6-7.
Table 6-16: SD Card Boot Time Optimization Register Setting Example
Register Security Value Description
slcr.ARM_CLK_CTRL Both 0x1F000200 CPU divisor = 2 (433 MHz)